The Atacama Large Millimeter Array will allow scientists to determine the radius and the rotation of stars and identify the chemical composition of dust being emitted from red supergiant stars (a star which is 10 to 1,000 times the diameter of our Sun, such as Betelgeuse).

One way in which a star is classified is by color (or spectra). Stars were first categorized in the 1890s by Annie Cannon. She used letters to classify the different spectra of light stars emitted. Originally the letters used were A through Q, since then, astronomers have narrowed and rearranged the classification index to the letters O, B, A F, G, K, M. O representing the hottest stars and M the coolest.

Below is a list of common stars and their attributes, the graph above represents how quickly the Atacama Large Millimeter Array will be able to detect these different stars.

Spectral Class	Color Emitted	Approximate Temperature	Star Example	Constellation
O	bluest	40,000K	Alnitak	Orion
			Mintaka	Orion
B	bluish	18,000K	Spica	Virgo
			Rigel	Orion
			Bellatrix	Orion
			Regulus	Leo
			Mimosa	Ursa Major
A	bluish-white	10,000K	Sirius	Canis Major
			Castor	Gemini
			Vega	Lyra
			Deneb	Cygnus
F	white	7,000K	Polaris	Ursa Minor
			Canopus	Carina
			Procyon	Canis Minor
			Dabih	Capricorn
			Sadr	Cygnus
G	yellowish-white	5,500K	The Sun
			Capella	Auriga
			Muphrid	Bootes
			Nekkar	Bootes
			Matar	Pegasus
K	orangish	4,000K	Edasich	Draco
			Kochab	Ursa Minor
			Izar	Bootes
			Dubhe	Ursa Major
			Pollux	Gemini
			Aldebaran	Taurus
M	reddish	3,000K	Betelgeuse	Orion
			Mirach	Andromeda
			Menkar	Cetaurus
			Antares	Scorpio
			Scheat	Pegasus